Window torsion balance units have been well known for a long time (see U.S. Pat. No. 2,580,705 issued in 1952). Such units ordinarily include a cylindrically-coiled torsion spring, enclosed within a cover or tube, and a twisted rod positioned within the coils of the spring. These units often rattle when the window is being raised or lowered; and such rattling can also occur in response to vibration created by passing trucks, slamming doors, high winds, etc.
Such rattling of torsion balance units is annoying, and it has been long recognized as a problem. Decades ago, felt washers were mounted on the springs as sound-deadeners (U.S. Pat. No. 2,877,514 issued in 1959). More recently, molded resin vibration dampeners have been mounted on the springs to space the springs from their covers (U.S. Pat. No. 4,540,070). Also, counterbalance springs have been flocked with fibers, and they have been covered with sound-deadening hot-melt thermoplastic polymer adhesives, as suggested in U.S. Pat. No. 4,854,558.
Another well-known method for reducing such annoying rattling has been to fill the balance cover with grease. However, this latter method has been less than satisfactory, since it has added significantly to the cost of manufacture: The grease must be appropriately sealed during the relative movement between the twisted rod and the encased spring; and it is difficult to find greases that are thick enough to prevent their leaking when ambient temperatures reach 74.degree. C. (100.degree. F.) and still remain sufficiently fluid so that they do not interfere with operation of the units when ambient temperatures drop far below freezing.
The invention disclosed herein is based upon a discovery that makes it possible to deaden the annoying rattling of torsion balance units with remarkably simple apparatus that can be manufactured in a relatively easy and economical manner.